To elucidate the change in frequencies and functions of myeloid dendritic cell (mDC) and plasmacytoid dendritic cell (pDC) before and after interferon-alpha therapy for chronic hepatitis B (CHB) patients, and its correlation with virological and biochemical data.Thirty patients with HBeAg-positive CHB who underwent IFN-alpha therapy were examined. Frequencies and expression of CD86 of mDC and pDC of peripheral blood were measured at baseline and treatment week (TW) 12 by flow cytometry. According to biochemical and virological parameters, the 30 patients were divided into ALT normalized group, ALT non-normalized group and virological responder group, virological non-responder group respectively. Statistical analysis of DC changes among different groups at baseline and TW12 was proceeded.(1) In the ALT normalized group, the pDC frequency at TW12 (0.25 +/- 0.14%) was higher than that at baseline (0.18 +/- 0.09%) (P = 0.023); in the ALT non-normalized group, the mDC frequency (0.58 +/- 0.34%) and its surface CD86 expression (61.80 +/- 22.52%) decreased significantly as compared with baseline (0.88 +/- 0.51%, 79.92 +/- 25.94%, respectively), (P = 0.025, P = 0.036, respectively). (2) In the virological responder group, the CD86 expression on pDC at TW12 (46.86 +/- 12.22%) was higher than that at baseline (29.42 +/- 15.16%) (P = 0.002); in the virological non-responder group, the mDC frequency (0.51 +/- 0.22%) and its surface CD86 expression (59.63 +/- 22.94% ) decreased significantly as compared with baseline (0.94 +/- 0.58%, 80.11 +/- 29.34%, respectively), (P = 0.006; P = 0.049, respectively).In IFN-alpha therapy for CHB patients, the increments of pDC frequency and function were related to biochemical and viral response, and decreases of mDC frequency and function were related to non-biochemical and non-viral response.